(The) development of under-display passive pixel vein sensor for smart device biometric recognition system

Abstract

This thesis presents a comprehensive study on the development and optimization of a passive pixel optical sensor (PPS) system, specifically tailored for creating a vein recognition system utilised in smart devices. The research focuses on the integration and performance analysis of various oxide thin film transistor (TFT) and organic photodiode (OPD) combinations within the PPS architecture, examining their photocurrent responses under different light conditions and operational states in individual unit cells. Key findings highlight the challenges and potential solutions associated with single-passivation TFT (SP-TFT) and solution-processed OPD (SP-OPD) configurations, including issues of non-uniformity and high leakage current. The study further explores the effectiveness of dual-passivation TFT (DP-TFT) and evaporation-processed OPD (EP-OPD) in enhancing system stability and uniformity. Other key focus areas include the analysis of interlayer dielectric (ILD) and black pixel define layer (BPDL) in PPS for optimal planarization, via hole development, and pixel isolation properties essential for high-resolution sensing. The integration of the PPS with readout integrated circuits (ROIC) and the analysis of ROIC readout under practical vein recognition scenarios are also meticulously investigated. The thesis demonstrates the feasibility and potential enhancements required for the PPS system, proposing future directions for improved vein pattern detection and recognition, and contributing significantly to the advancement of biometric recognition technology in smart devices.